Among all this, my opinion is....GREAT! And if Scarlet Witch also appears... GREATER!(i wish it happens). I prefer them in X-men.
It makes all sense..they first appear in X-Men and then Avengers i think, so the same way with the movies...love the fact they are mutants and magneto children..bring Polaris..

well of course they were not Magneto's children when first introduced in 1964 - and around 1974 they were established as being the children of two Golden Age heroes [the Whizzer and Ms. America] - not sure when all this was tossed out the window in favor of Magneto being their dad...